Removal tool for recessed head screws



Dec. 3, 1957 L. A. CUMMARO ,8 4

REMOVAL TOOL FOR RECESSED HEAD SCREWS Filed Sept. 8, 1953 INVENTOR.

LOUIS A. CUMMARO ATTORNEYS REMGVAL TOOL FOR RECESSED HEAD SCREWS Louis A. Cummaro, Bronxville, N. Y., assignor to Phillips Screw Company, New York, N. Y., a corporation of Delaware Application September 8, 1953, Serial No. 379,007

7 Claims. (Cl. 145-50) The present invention relates to a tool adapted for use in removing screws and like threaded fastening devices having a driver engaging recess in the head thereof which has been damaged to such an extent that the usual driver cannot be used to effectuate removal of the device.

Recessed head screws, of the type shown for example in the Patent 2,046,839Phillips, have certain well known advantages insofar as driving is concerned, but are difiicult to remove with tools available heretofore if the recess defining portions are damaged during the driving operation. Most power screw drivers are provided with an overload clutch which may be adjusted to slip before the driving torque is great enough to damage the recess, but unfortunately these clutches are subject to a number of variables so that they cannot always be given or maintained at an exact setting. Also operators are inclined to set the clutches to slip at too great a torque rather than too little to be sure of driving all screws completely home. Thus occasionally the recess of the screwhead is reamed out after the screw has been driven home whereupon the driver is permitted to rotate freely relative to the screw recess. When this occurs it is impossible, of course, to remove the screw with the usual driver since there is nothing against which the driver wings may gain a purchase to rotate the screw.

Heretofore it has been the practice to drill out the damaged screws. It will be apparent, however, that this is not satisfactory since a great deal of care and time are necessary to avoid injuring the structure into which the screw has been driven.

It is an object of the invention to provide a new and improved tool for removing threaded fastening devices.

Another object is to provide a tool which is adapted for use in removing damaged recessed head type screws without injury to the structure into which the screw is driven.

A further object of the invention is to provide a tool of the class described adapted for facilitating quick and easy removal of screws having a damaged head recess.

Other objects and advantages of the invention will become more apparent hereinafter.

In accordance with an illustrated embodiment, the tool of the present invention comprises a shank having a bit formed at one end thereof, the opposite end of the shank being adapted to be secured in a power tool or hand driver. The bit is of cruciform cross-section comprising alternate flutes and vanes each of which vanes is provided with a driving thrust face adapted to transmit a driving torque to the head of a screw to remove the same. The free end of the bit is provided with a symmetrical recess to form a sharp point on each of the vanes whereby the bit may be engaged in the reamed out head of the screw by placing the bit in engagement therewith and tapping the opposite end of the tool to drive the points of the vanes into the base of the recess cavity, following which, upon application of torque, the bit will bite firmly into the recess side walls to permit removal of the screw.

For a more detailed description of the invention, refernited States Patent ICE ence is made to the following specification taken in conjunction with the accompanying drawing wherein:

Fig. 1 is a top plan view of a screwhead provided with a cruciform tool receiving recess;

Fig. 2 is a side elevation of the bit portion of a driver adapted for use with screws having a cruciform recess such as shown in Fig. 1;

Fig. 3 is a fragmentary perspective view of a screw such as shown in Fig. 1 and in which the driver receiv ing recess has been reamed by reason of twisting of the driver relative to the screw;

Fig. 4 is a side elevation of the bit of the tool of the invention;

Fig. 5 is a side elevation of the bit rotated 45 degrees relative to the position of the tool in Fig. 4;

Fig. 6 is an end view of the tool of the invention;

Fig. 7 is a vertical section substantially on line 7-7 of Fig. 6 showing the tool positioned in a recess of a screwhead sectioned in the plane of the section of the tool; and

Fig. 8 is an end view of a bit formed in accordance with a modification of the invention.

For purposes of simplicity, the present invention will be described as adapted specifically for use in removing screws provided with a Phillips type recess, although it will be obvious that the invention is equally applicable with screws having heads of other types. In Fig. 1 is shown a flat headed screw provided with a recess of the Phillips type and generally indicated by the reference character 10. This recess is of cruciform shape in plan, generally conical in vertical section, and includes a plurality of radially extending slots or grooves ll and intermediate ribs 12. The outer end walls 14 of the grooves 11 are inclined inwardly toward the axis of the recess at the bottom thereof. Such screws are adapted to be driven by a driver 15 having a bit complementary in form and size as shown in Fig. 2. When a driver is driven with such force after the screw is driven home that it reams out or burrs over the ribs or ridges 12 driving engagement of the driver and the screw cannot be obtained to remove the screw from the work in which it is engaged. A typical reamed out screw recess is shown at 16 in Fig. 3.

Referring now to Figs. 4, 5 and 6, the screw removal tool of the present invention comprises a shank 20 having a bit formed on one end thereof. In certain respects, the bit of the present tool is similar to the bit of the driver shown in Fig. 2 in that it comprises a plurality of vanes 24 and intermediate flutes 25. The side wall on the side of each vane facing in the direction of rotation of the tool to unthread a screw is indicated by the numeral 26 and will hereinafter be referred to as the forward or driving face. The opposite side wall 27 of each vane will be referred to as the rear face. Each of the vanes 24 is also provided with a planar outer wall or end surface 28 that intersects the driving face 26 along a sharp edge 29 inclined toward the axis of the bit at approximately the same angle as the outer end wall 14 of the screwhead recess. In other words, the inwardly tapered vane end edges 29 define a conico-frustum end configuration for the bit substantially conforming to the conical, reamed out recess 16 as illustrated in Fig. 3. The end surface 28 is also inclined inwardly of the bit from its intersection with the driving face 26 at an angle of about 4-5 degrees in respect to the longitudinal plane of the vane, whereby the end surface 28 and the driving face 26 define an acute dihedral angle.

To form a sharp point 30 on the end of each of the vanes 24,. the free end of the bit is provided with a recess. This pyramidal recess may be provided by a pair of right angular V-shaped notches 32 in the free end of the bit symmetrically disposed in respect to the bit axis, which notches extend transversely of the free end of the bit and at right angles in respect to one another. The apices 33 of the notches 32 are perpendicular to and intersect the bit axis and substantially bisect the flutes 25, but are preferably inclined at a small acute angle 34 such as, for example, an angle of about 15 degrees, from the flute center line toward the rear face 27 of the adjacent vane. The crossed notches 32 provided in the end of the bit result in the sharp pyramidal point 30 on each vane adapted to be driven into the reamed out body of a screwhead.

The modified bit illustrated in the end view of Fig. 8 is of similar construction to the previously described embodiment with the exception that the end recess of the bit is formed by cutting or grinding a coaxial conical recess 35 therein thereby defining with the vane driving face 26 and end surface 28 a point 36 on each of the vanes 24.

To extract a screw with the tool of the present invention, the bit is inserted into the recess cavity and the end of the tool or shank is tapped or struck with a suitable instrument to drive the points 30 into the body of the screwhead as shown in Fig. 7. The shank is then engaged in a power tool or otherwise turned in the proper direction to unthread the screw, driving purchase against the screw being provided by reason of the driving faces 26 of the vanes. The sharp angle provided on the edges 29 of the driving faces causes them to bite into the body of the screw rather than to cam out, thus facilitating retention of the bit in engagement with the screw to elfect removal of the screw. Axial thrust should be maintained upon the tool, of course, to assure retention of the bit in engagement with the head of the screw.

Having illustrated and described preferred embodiments of the invention, it should be apparent to those skilled in the art that the invention permits of modification in arrangement and detail. 1 claim as my invention all such modifications as come within the true spirit and scope of the appended claims.

I claim:

1. A screw removal tool comprising a bit of polygonal cross-section, defined by alternate flutes and vanes, said vanes at the end of said bit having peripheral surfaces conically tapered inwardly toward the axis of said bit, the end of said bit having a recess therein, said vanes terminating at sharp points spaced outwardly from said axis.

2. A screw removal tool comprising a shank having a bit of cruciform cross-section formedat one end thereof, said bit comprising alternate flutes and vanes, each of said vanes being formed with one substantially radial driving face adapted to transmit driving torque to the screwhead upon rotation of said bit in the unscrewing direction and an outer end face intersecting said driving face to define an outer end edge, said outer end edges tapering inwardly at the end of said bit toward the longitudinal axis of the bit in the direction away from said shank, the free end of said bit being recessed to define on each of said vanes a sharp point spaced from the axis of the bit.

3. A screw removal tool comprising a shank portion having a bit formed at one end thereof, said bit comprising a plurality of radially arranged alternate flutes and vanes, the end of said bit having a substantially pyramidal recess therein, each of said vanes having a driving face and an outer end face defining a sharp outer end edge inclined inwardly toward the longitudinal axis of the bit in the direction away from said shank portion.

4. A screw removal tool comprising a shank having a substantially cruciform bit formed on one end thereof, said bit comprising a plurality of alternate flutes and vanes, each of said vanes having one planar driving face adapted to exert a driving torque to the screw upon rotation thereof, each of said vanes having an outer planar end surface at the free end of the bit inc lined toward the longitudinal axis of the bit, each of said end surfaces being further inclined in respect to the corresponding vane driving face whereby the driving face and outer end surface of a vane define an acute dihedral angle, the free end of said bit having a substantially symmetrically converging recess therein whereby each of said vanes terminates in a sharp point defined in part by the driving face and outer end surface of the vane.

5. A tool of the class described comprising a shank portion and a bit portion formed on one end thereof, said bit portion comprising a plurality of radially arranged alternate flutes and vanes, each of said vanes having a planar driving face, each of said vanes having an outer planar end surface at the free end of the bit inclined toward said longitudinal axis, each of said end surfaces being further inclined in respect to the corresponding vane driving face whereby the driving face and outer end surface of a vane define an acute dihedral angle, the free end of said bit having a substantially symmetrically converging recess therein whereby each of said vanes terminates in a sharp point spaced outwardly from the axis of said bit and defined in part by the driving face and outer end surface thereof.

6. A tool for use in removing a screw having a damaged cruciform shaped driver engaging recess in the head thereof, said tool comprising a shank portion and a cruciform shaped bit portion formed on one end thereof, said bit portion comprising alternate flutes and vanes, each of said vanes being formed with one driving face and an opposite rear face, each of said vanes having an outer end surface extending between said faces inclined toward the axis of said bit, the included angle through each vane between each driving face and the adjacent end surface being substantially less than degrees whereby said driving face and end surface intersect at a sharp end edge, said sharp end edges of all of said vanes lying in a common conico-frustum surface.

7. A tool for removing damaged recessed head screws and like threaded fastener devices, said tool having a bit of cruciform cross-section formed on one end thereof, said bit comprising a plurality of alternate flutes and vanes, each of said vanes having substantially parallel opposite side walls, one of said side walls of each vane defining a driving face, each of said vanes having an outer, planar surface at the free end of the bit inclined toward the axis thereof, each of said surfaces being further inclined with respect to said driving face such that the included angle between said planar surface and the corresponding adjacent driving face is an acute angle of approximately 45 degrees, said bit having a pair of symmetrically disposed right angular V-shaped notches extending transversely of the free end of said bit and at right angles in respect to one another, the apices of said notches substantially bisecting said flutes, whereby each of said vanes is formed with a sharp protruding point thereon, the points on each of said vanes being spaced a substantially equal distance from the axis of said bit.

References Cited in the tile of this patent UNITED STATES PATENTS 173,356 Sloan Feb. 8, 1876 839,105 Butler Dec. 25, 1906 1,547,944 Murphree July 28, 1925 1,899,489 Wickbergh Feb. 28, 1933 1,908,081 Thompson May 9, 1933 2,046,837 Phillips July 7, 1936 2,369,853 Purtell Feb. 20, 1945 2,601,453 Phipard June 24, 1952 FOREIGN PATENTS 201,705 Switzerland Mar. 1, 1939 241,061 Switzerland June 1, 1946 

